The present invention relates to a magnetic tape cassette having improved magnetic tape guides which, when brought into contact with the magnetic tape, guide the latter.
A magnetic tape cassette employed in an audio or video playback and/or recording device has magnetic tape guides which are arranged to be brought into contact with the magnetic tape to guide the latter. The tape guides are provided so as to contact the tape's rear side (base side). The tape guides are usually formed integrally with the cassette case. Alternatively, the tape guides can be provided as separate plastic resin or metal components which are fixedly mounted in the cassette case.
Most commonly, the above-described tape guides are in the form of a pipe-like hollow cylinder or in the form of a solid cylinder. On the other hand, because recently magnetic tape cassettes and recording and reproducing devices have been improved in performance and high-density recording and reproducing operations are required, tape guides made of a metal such as stainless steel have been used to maintain the tape running characteristic relatively satisfactory for long periods of time. However, the metal tape guide is disadvantageous in that it has a high manufacturing cost because its material is expensive, and moreover a heat treatment for increasing the hardness of the guide or a surface treatment for improving its surface characteristic is difficult to perform.
A tape guide formed integrally with the cassette case is of course made of the same material as the cassette case, usually a plastic resin such as acrylonitrile butadiene styrene (ABS) resin, acrylonitrile styrene (AS) resin or polypropyrene (PP) resin. A tape guide fixedly mounted in the cassette case, on the other hand, is often made of polyoxymethylene (POM). These tape guides suffer from the following difficulties:
As is well known in the art, a magnetic tape is manufactured with a strengthened and rolled polyester film as its base. Therefore, when the tape guide of plastic resin is brought into frictional contact with the tape's rear side, the tape guide is electrically charged, causing electrostatic attraction of the tape. As a result, the tape running characteristic is often less than satisfactory. If the tape guide is highly charged, the tape may even be stopped. This is a serious drawback.